- 學位論文
Oxygen Exposure And Surface Oxidation Of Ni/Cu(001) Ultrathin Films
Oxygen Exposure And Surface Oxidation Of Ni/Cu(001) Ultrathin Films
摘要
本實驗是在探討鎳金屬(Ni) 磁性超薄膜接受不同壓力條件下進行曝氧，並分析其所產生的氧化鎳(NiO) 對應其鐵磁層與反鐵磁層之間磁性變化關係。我們使用中能電子繞射(medium-energy electron diffraction, MEED) 跟蒸鍍槍去成長所需要10ML的鎳金屬磁性超薄膜在基板Cu(001)上，接著對磁性超薄膜在P=1×10-5 mbar、P=1×10-6 mbar、P=1×10-7 mbar和P=1×10-8mbar四種不同壓力條件下曝相同的總曝氧量18000L， 接著再使用低能電子繞射(low energy electron diffraction, LEED) 研究晶格結構的變化，磁光柯爾效應(magnetic optic Kerr effect, MOKE) 研究磁性關係。我們也從磁性的角度分析發現到超薄膜表面會因此生成不同厚度與不同磁性耦合程度的氧化鎳，其氧化鎳會產生反鐵磁的磁性，進而影響到下方的鐵磁層磁性。同時我們發現在P=1×10-5 mbar、P=1×10-6 mbar和P=1×10-7 mbar所形成的氧化物會有飽和的現象並在超薄模表面形成氧化鎳的保護層，而在P=1×10-8 mbar卻會繼續影響下方的鐵磁層，這意味著鎳金屬超薄膜必須在P=1×10-7 mbar以上的壓力才會形成保護層，相反的在P=1×10-8 mbar以下則會繼續生成更厚的氧化鎳。
並列摘要
The pressure effect of the oxygen exposure on the magnetism of Ni/Cu(001) is investigated for understanding the magnetic properties of ferro-antiferromagnetic(FM/AF) interlayer coupling. The films were prepared by deposition of Ni in an ultrahigh vacuum chamber with base pressure of 5×10-10 mbar. The thickness was chosen to be ten for the various magnetic transitions occurred at this thickness. The oxygen exposure was designated at P=1×10-5mbar,P=1×10-6mbar,P=1×10-7mbar and P=1×10-8mbar and followed by P=1×10-5mbar for saturated oxidation. It is found that oxygen exposure will reduce the residual magnetism above P=1×10-7mbar, but there is still magnetic. With the increase of oxygen exposure, magnetic will be reduced until there are no magnetic below P=1×10-8mbar. The results indicate that the oxidation proceeded at the pressure above P=1×10-7mbar that results in a protection layer. In contrast, the pressure below P=1×10-8mbar diminishes the magnetism. It implies that the formation of the protected oxide layer requires a pressure higher than ,P=1×10-7mbar, below which the oxidation is not completed neither does the protection.